The present invention relates to selecting communication paths in a processing system between a subsystem and external devices. In particular, embodiments relate to maximizing communication efficiency between a subsystem and external devices by prioritizing communication paths based on initial command response times of I/O operations on the paths.
Processing systems communicate with external devices via one or more paths made up of switches and interconnection circuitry between a communication channel of the processing system and an I/O port of the external device. When multiple paths connect the processing system to the external device, the processing system may alternate which path is used to communicate with the external device. When one or more paths becomes congested due to resource contention, storage area network congestion, control unit port congestion, I/O firmware failures, or I/O hardware failures, the operation of the processor may be degraded when communication paths are routed via the congested path.